How do I make animations a steady speed?
Simply go to the Animation Screen Layout:



Now select Channel > Extrapolation Mode > Linear Extrapolation (shortcut Shift + E):



And that should fix it for you.

If you look at the Graph Editor before doing this, you will see:



The beginning and end of the curve are levelled out, this is what gives you the slowing down effect. It is called a Bezier function. When you choose 'Linear Extrapolation' it makes the curve a straight line:

 

The straight line is extended in both directions giving you continued animation, whereby if you choose Interpolation, Key > Interpolation Mode > Linear (shortcut T):



What starts off as curves...



...results in straight lines between keyframes with no extension beyond: